The cardiovascular system

What is the Pulmonary pathway of blood

De-oxygenated blood to the lungs, Oxygenated blood to the heart

What is the systemic pathway of blood

Oxygenated blood to the body, De-oxygenated to the heart

Describe the pathway of blood

1. Deoxygenated blood enters the Right Atrium

2. Right Atrium contracts forcing open the Tricuspid valve, sending deoxygenated blood into the RV

3. Right Ventricle contracts forcing open semi-lunar valve sending de-oxygenated blood to the lungs (carried by the pulmonary artery)

4. Oxygenated blood is carried back to the heart by the pulmonary vein

5. Oxygenated blood enters the left atrium

6. Left atrium contracts forcing the bicuspid valve to open, sending oxygenated blood to the left ventricle

7. Left ventricle contracts forcing open the semilunar valve which sends oxygenated blood through the aorta as it is carried to the body

 

What are the components of the Cardiac conduction system

1. Sinoatrial node (SA node)

2. Atrioventricular node (AV node)

3. HIS bundle

4. Purkinje fibres

What is the function of the Sinoatrial node/ SA node

 a small mass of cardiac muscle found in the wall of the right atrium that generates the heartbeat

What is the function of the Atrioventricular node (AV node)

this node relays the impulse between the upper and lower sections of the heart (delays impulse to allow the full contraction of the atrium and the filling of the ventricles) delay of 0.1secs to allow contraction to finish

What is the function of the bundle of HIS

 a collection of heart muscle cells that transmit electrical impulses from the AV node via the bundle branches to the ventricles

What is the function of the Purkinje fibres

 muscle fibres that conduct impulses in the walls of ventricles

What does myogenic mean

 the capacity of the heart to generate its own impulses

What does systole mean

 when the heart contracts

blood is expelled from the chambers of the heart

What does diastole mean

the phase of the cardiac cycle where the heart muscle relaxes allowing the chambers to fill with blood

Describe the process of the cardiac conduction system

Describe what happens at each stage of the cardiac cycle

Stage of cardiac cycle	Description	Action of valves
Atrial Diastole	Atrium relaxes Fills with blood	AV valves close SL valves open
Ventricular Diastole	Ventricle relaxes Fills with blood	AV valves open Semi lunar valves close
Atrial Systole	Atrium contracts Blood is forced out	AV valves open SL valves close
Ventricular Systole	Ventricle contracts Blood is forced out	Semi lunar valves forced open  AV valves closed

What does the sympathetic nervous system do

stimulates the heart to beat faster

What does the parasympathetic nervous system do

returns the heart to it’s resting level

PARACHUTES SLOW THINGS DOWN

What is the MEDULLA OBLONGATA

• located in the brain is the cardiac control centre

what are the 3 main mechanisms of the medulla oblongata

1. chemoreceptors

2. baroreceptors

3. Proprioceptors

What is the function of chemoreceptors

Found in the carotid arteries and the aortic arc

• they Sense chemical changes => Detect the increase in C02 when exercising

• The increase in conc. will effect the stimulation of the sympathetic nervous system which means the heart will beat faster

What is the function of baroreceptors

they Contain nerve endings which respond to the stretching of the arterial wall caused by changes in blood pressure

• If a change occurs signals are sent to the medulla

• Increase in pressure = increase in stretch of baroreceptor sensors = decrease in HR

• Decrease in pressure = decrease in stretch = increase HR

• When exercise starts the set point increases to prevent the reduction of HR and a negative impact on performance (less oxygen delivered)

What is the function of proprioceptors

they are Sensory nerve endings located in the muscles, tendons and joints - provide info on movement and body position

• they Detect increase in muscle movement

• They trigger impulses to the medulla => sends impulse through the CNS to the SA Node to increase HR

• When the PNS stimulates the SA Node, HR decreases

In short what does each mechanism do

Chemoreceptors	DETECT: Increase in CO2	RESPONSE: Increase in HR
Baroreceptors	DETECT: Increase in BP	RESPONSE: Decrease in HR
Proprioceptors	DETECT: Increase in muscle movement	RESPONSE: Increase in HR

What is the hormonal control mechanism

• it effects HR

• Adrenaline - the stress hormone

• Released by the sympathetic nerves and cardiac nerve during exercise

• Stimulates the SA Node resulting in an increase in speed and force of con traction

• this Increases cardiac output

• Which results in more blood being pumped to the working muscle